What is the Three Sisters Planting Method?

The Three Sisters Planting Method is an ancient practice dating back to almost three hundred years ago. Native American tribes such as the Iroquois and Cherokee grew Three Sister Gardens as it allowed them to successfully grow 3 crops in the area of one.  The Three Sisters Planting Method is an equally important gardening concept today as it was all those years ago as it provides long-term soil fertility whilst maximising growing space. It is a form of sustainable gardening as increases biodiversity, attracts pollinators and enhances soil fertility rather than removing it.

The Three Sisters Planting Method is essentially the companion planting of sweetcorn, climbing beans and pumpkin or squash on the same plot or within close proximity to one another.

When most people think of companion planting it is usually to add crops that smell strongly and deter predators. For example, planting mint beside lettuce to keep snails away, marigolds with tomatoes etc.  The Three Sisters planting method is an example of companion planting at its’ best. Inside a Three Sisters plot each plant contributes and thrives from being near to the others, working symbiotically to deter weeds and pests, whilst enriching the soil.

How does the Three Sisters Method Work?

The Three Sisters Method works by each 'sister' contributing to the crop growth. It’s not dissimilar to plant growth in a jungle or even your local woodland which, consists of many different plants harmoniously growing under, over and around each other.  This growing method is the same: each plant has its place and thrives without a gardener wringing their hands and fretting about how to keep pests away.   

The first of our Three Sisters is sweetcorn which grows tall and strong  providing a structure for the beans to climb up. 

You can substitute for sunflowers if you don't like corn.  Sunflowers do have the advantage of attracting lots of lovely pollinators and provide you with sunflower seeds at the end too. Sometimes sunflower plants are added as a fourth sister not only for pollination purposes but as a sacrificial decoy plant to lure birds away.

The beans return the love by stabilising the corn so that it doesn't snap in the wind.  They also fix the nitrogen into the soil that the other plants need and take up space between the corn stems reducing the space available for weeds.  

Lastly the sprawling squash plants block sunlight on the soil, effectively creating a living mulch. This helps reduce soil temperatures, minimise moisture loss and suppress weed growth. The prickly squash leaves also help keep little critters out.

Which varieties are best for the Three Sisters Method?

The corn should be a tall variety so that it gives the beans somewhere to climb.  More compact varieties are usually grown here but look for the taller varieties otherwise you may find the beans overcrowd the corn. Taller varieties stand tall which ensures successful wind pollination.
Beans must be pole or climbing varieties rather than bush beans.  Non-vigorous and bushy-pole are best as they don't smother the corn plants. This is important because if the beans grow too vigorously, they can pull corn stalks over. Beans that do work very well include Climbing French Beans, Lima, Runner Beans and Borlotti Beans.

If you are fortunate enough to have limitless space (lucky you) then winter squashes will work otherwise stick to summer squashes which are a little more contained.  Squashes can be substituted with watermelons, gourds or courgettes although it may be wise to steer clear from pumpkins as these can grow too vigorously and can be too heavy for the other crops to cope with.

How much space is required for the Three Sisters Method?

Ideally, you need an area a minimum of 3 x 3 metres (10 x 10 feet) although a single 3 Sisters Mound could fit into 1 x 1 m (3 x 3 feet). However, if you do try the method on a smaller scale it is advisable to either do more than one mound or avoid sweetcorn as you need 10 to 20 plants to ensure full pollination and achieve full cobs. 

Does the soil need to be prepared for the Three Sisters Planting Method?

Prior to any planting prepare your soil. It is highly important that your soil has enough nutrition as these plants grow and produce crops rapidly in a short space of time. Corn requires lots of nitrogen and while the beans provide this during the growing period, your plot may benefit from it being introduced into the soil before the planting begins. If this companion system has been planted on this plot previously then this is something you do not need to worry about. The nitrogen from the previous crop will still be present. In fact, it is possible to grow these three plants together for a number of years in the same place.

How to plant the Three Sisters Method

Getting this method right is all about timing. Your uprights or supporting plants such as the sweetcorn or sunflowers need a three-week head start so that they are strong enough to support your beans. Prior to this it is advisable to support them with a stake.

All the seeds can be planted directly into the ground. However in order to ensure the roots have a super strong root system it is advisable to start them off in Rootrainers.

This will prevent holes in your planting scheme from seeds that fail to germinate. The good thing about 3 Sisters is that you can use one set of Deep Rootrainers for all three crops in turn.  

Make a mound of soil about 10cm (4") high with a small well in the centre.  Repeat this at 1-1.2M (3-4') intervals for as many mounds as you want to construct. 

For each mound - plant 4 corn seeds in Rootrainers and wait until they are about 12cm (5") tall.  Then move 4 plants to the top of your prepared mound and plant there 15cm (6") apart.

Once the corn is in the ground, plant 4 beans seeds in your Rootrainers.  When your beans are large enough to transfer, plant them halfway down the sides of the mound at least 7cm (3") from the corn plant. 

The beans will grow slowly at first as they will be shaded by the corn, but this is a delay rather than a full stop and they will catch up and make a spurt in growth as the sweetcorn matures.

Finally use your Rootrainers for 2 squash seeds.  Once these are large enough to transplant plant them opposite each other 60cm (24") from the centre of the mound.  Squash plants need as much light as they can get, hence planting on the outside of your arrangement.  Unless you are gardening in a stately home then choose a compact variety and leave some natural paths so you can reach the inner plants to pick them. 

If you don't like squash then, whilst not quite as leafy and prolific, courgettes, gourds or even watermelons would fulfil a similar role around the outside.  Check out our guide to each of there here:

How to Grow Watermelons

How to Grow Courgettes      

The good thing about this method is that it is actually good for the soil and works best if you don't do crop rotation.  The breakdown of the bean roots from last year’s crop fixes the extra nitrogen that the corn needs into the soil.

Can I introduce another plant into the Three Sisters Planting Method?

Some gardeners believe introducing an additional sister can have a beneficial impact. Adding a flowering plant can encourage pollinators, deter pests or used as culinary herbs. Suitable herbs include rosemary, thyme and chives. Flowering plants can also be used as a sacrificial plant for snail and slugs to eat instead of your vegetables. .

We'd love to see it if you plant a 3 Sisters Garden.  Please tag us on Social Media if you decide to try it.